According to the Biot and Savart law, when two heavy nuclei are doing peripheral or non-central collisions in heavy ion collisions (HIC) experiments, a huge magnetic field can be produced. Its values are expected approximately \(m_\pi ^2\)  in RHIC energy and \(10 m_\pi ^2\)  in LHC energy [1]}. The order of magnitude of this magnetic field (\(1-10 m_\pi ^2\approx 10^{18}-10^{19} G\) ) is perhaps the strongest magnetic field that has ever existed in nature. However, it will decay with time, whose detailed time profile (including space profile) are investigated in Refs. [1]}, [3]}, [4]}. The decay time with respect to QGP life time will basically fix whether QGP face strong [1]} or weak [6]}, [4]} magnetic field which is not approached towards converging conclusion probably.
